Abstract: Disclosed is a curable formulation comprising a resin; all, or a substantial part, of which comprises one or more fatty acid esters, or their derivatives, obtained from plant oils. Due to the high viscosity of known curable resin materials, and in particular cationically photocurable and thermally curable resins epoxy resins, reactive diluents are conventionally added in order to reduce viscosity and render them suitable for certain methods of application, such as flexography and inkjet printing. However, if an excessive amount of reactive diluent is added to a formulation, the concentration of resin may be so low as to prevent a formulation from curing to form a cured, cross-linked material with acceptable properties. Thus the minimum viscosity of known formulations is limited by the amount of low viscosity reactive diluent which may be added to comparatively high viscosity resins.